1. Field of the Invention
The present invention relates to a metallized film capacitor for improving power factor, an electric appliance, several kinds of power source circuit and communication device, a device and method for fabricating a metallized film used for the metallize film capacitor.
2. Description of the Related Art
Conventionally, a capacitor equipped with a fusing mechanism by minute division of evaporated metallized film or using the metallized film is disclosed in Japanese Patent Unexamined Publication Nos. Hei 4-225508, Hei 8-31690, etc. Therefore, it is possible to fabricate a metallized film capacitor equipped with the fusing mechanism.
A previously known method of fabricating a metallized film for a capacitor is shown in FIG. 13. In this method, as shown in FIG. 16, immediately before an evaporated metal 15 is evaporated, in a vacuum evaporator, on a plastic film 10 (high polymer film) at a position where the film is brought into contact with a cooling roll 12, it is passed through an oil depositing device so that a plurality of divided margins serving as a safeguard mechanism is formed in a longitudinal direction of the plastic film (Japanese Patent Unexamined Publication No. Hei 57-152122). The apparatus used for this purpose includes an oil tank 14 that contains oil 27 therein and a shutter 28 rotating around the oil tank 14. The oil 27 within the oil tank 14 is heated and vaporized. When an opening 31 of the oil tank 14 and another opening 30 of the rotating shutter 28 coincide with each other, the oil passes through the openings 31 and 30 to be deposited on the plastic film 10. In this case, since the rotating shutter 28 rotates in synchronism with the supplying speed of the plastic film 10, the oil 27 can be deposited on the plastic tape at regular widths and intervals.
Another previously known method for fabricating a metallized film is shown in FIG. 14. In this method, a convex type roll 33 with protrusions 32 formed on its circumference at given positions is used. A metal evaporation preventing substance (e.g. oil) 27 deposited on the surface of the protrusions 32 are transferred onto a plastic film 10 to form non-evaporated portions (Japanese Patent Unexamined Publication No. Hei 6-158271) thereon. Still another previously known method for fabricating a metallized film is shown in FIG. 15. In this method, using a concave type roll 35 with grooves 34 formed on its circumference, a metal evaporation preventing substance (e.g. oil) deposited on the surface of the grooves 34 are transferred onto the plastic film 10 to form non-evaporated portions thereon (Japanese Patent Unexamined Publication No. Hei 4-346652).
A further previously known method for fabricating a metallized film is shown in FIG. 11. In this method, in an evaporation step, margins of a tape at regular widths and intervals are evaporated in a direction parallel in the longitudinal direction of the tape by the oil masking technique and-tape margin technique, and in a post step, a plurality of divided electrodes and fuse portions are formed in the longitudinal direction by laser trimming and discharge machining.
The metallized film capacitor fabricated by the methods as described above suffers from several problems. In a configuration shown in FIG. 11 in which a metallized electrode is divided into plural minute blocks 8 and fuse areas 9 are arranged between the blocks, where minute breakage which cannot be cleared by self-recovery occurs, an excessive short-circuiting current flows so that the pertinent fuse area 9 operates to separate the broken portion from the metallized film capacitor. But since its area is minute, the current circulating from between the adjacent minute blocks causes the fuse area therebetween to be also operated, thus reducing the capacitance of an non-problematic portion.
Further, where the fuse area 9 does not operate by the short-circuiting current by clearing the minute breakage, the breakage at the block continues to lead to dielectric breakdown. Further, the breakage might spread toward the surrounding blocks. In the worst case, the metallized film capacitor might catch smoke or fire.
Further, as shown in FIG. 12, in the metallized film capacitor equipped with a safeguard mechanism, in many cases, in order to improve the contact force between a metal sprayed area serving as an electrode lead-out portion and a metallized film, the thickness of an evaporating film at the metal sprayed area side is made thicker whereas that of the remaining portion is made thinner. At least one of the evaporating films is divided by electrode partitioning lines 7 to form the fuse area 9. In this case, the safeguard mechanism, when the breakage that cannot be cleared by self-recovery which is inherent to a film capacitor occurs, serves to operate the fuse area 9 using the Joule heat of the short-circuiting current for clearing the broken portion. But, where the breakage which cannot be cleared because of the thick film evaporated in the metal sprayed area, which requires higher energy for its clearing than the remaining portion does, the short-circuiting current continue to flow. Thus, the dielectric breakdown might occurs at the thick evaporated film.
However, the techniques for forming the non-evaporated portion suffer from several problems to be solved.
Where the metallized film capacitor with the safeguard mechanism is to be fabricated using the rotary shutter 28 as shown in FIGS. 13 and 16, as the case may be, in view of the property of a capacitor, the electrode of the evaporated film must be not only divided in plural blocks in a longitudinal direction of the plastic film, but also a square non-metallic island (fuse area) must be simultaneously formed in each of the divided electrode blocks. In this case, when the divided blocks and fuse areas are to be formed using the rotary shutter 28, only the slender fuse areas in the width direction of the film serve as relay portions of the rotary shutter 28. When the evaporation is carried out at a high speed, therefore, the rotary shutter 28 is apt to be deformed and the divided blocks and fuse areas are likely to be unclear. For this reason, the speed of evaporation could not be increased. Further, if a means is adopted which uses a difficult-to-deform substance for preventing the rotary shutter 28 from being deformed and increase the thickness, workability is deteriorated because of the problem of weight. In addition, in this case, the margin in a longitudinal direction must be formed at a separate portion by the oil masking method and tape margin technique. The adjustment required therefor might deteriorate the workability further greatly.
The technique using the convex type roll 33 as shown in FIG. 14 provides the following problem occurs. When the metal evaporation preventing substance (e.g. oil) 27 is deposited to the protrusions 32 to form the non-evaporated margin, i.e. island-like divided electrode are formed in the longitudinal direction of the plastic film 10 and provide the electrodes with a fusing function, because of the centrifugal force of the convex type roll 33, the oil 27 scatters to provide a spot-like evaporated film and blur of the margin. This make it impossible to increase the evaporation speed.
The technique using the concave type roll 35 permits the evaporation speed to be increased. However, this technique has disadvantages that the cost of the concave type roll (pattern roll) 35 is expensive, and attachment/detachment of the concave type roll 35 in exchange is difficult owing to the problem of weight.
The technique shown in FIG. 13, in which in an evaporation step, margins are evaporated at regular widths and intervals in a direction parallel in the longitudinal direction of the tape and in a post step, a plurality of divided electrodes and fuse areas are formed in the longitudinal direction by laser trimming and discharge machining, provides economical and time loss because of an additional one step as compared with the other techniques.